1

Sponsored byThe Institute of Electrical and Electronics Engineers (IEEE)

Ultrasonics, Ferroelectrics and Frequency Control (UFFC) Society

U

2005-2006 International Distinguished Lecturer Program

Ken-ya HashimotoChiba University

2

Introduction to RF SAW/BAW Filters

Ken-ya HashimotoChiba University

k.hashimoto@ieee.orghttp://www.em.eng.chiba-u.jp/~ken

3

RF Filter Basics RF SAW and BAW Devices Major Players

ContentsContents

4

RF Filter Basics RF SAW and BAW DevicesRF SAW and BAW DevicesRF SAW and BAW Devices Major PlayersMajor PlayersMajor Players

ContentsContents

5

Mobile Phone market

Source: Prismark report March 2005

6

Evolution of component count in a Mobile Phone

7

Suppression of Spurious in Power Amplifier (PA) Output

RF-BPFPA

Role of Tx FiltersRole of Tx Filters

ωfrequency

Spec

trum

Tx RxInterferer

Output Power Reduction by 20% through Insertion loss IL of 1dB

Current Consumption

Heat Generation

Ultimate IL Reduction Necessary!

8

Role of Rx FiltersRole of Rx FiltersInterferer Suppression in Out-of-Band to Avoid Saturation, Mixing, etc.

RF-BPF LNA

ωfrequency

Spec

trum

ωfrequency

Spec

trum

ωfrequency

Spec

trum

Frontend Stage is Most Important (Low Loss + Low Noise)

9

Typical situation in a phone Strong interference from other phones and

own Tx signal

f[MHz]1850

19101930

19902450

Tx Rx ISM

US-PCS

wantedRx

120 dB lower !signal

level

GPS

10

Highly selective RF-filters needed

f[MHz]1850

19101930

19902450

Tx Rx ISM

US-PCS Rx filterattenuation[dB]

0

10

20

30

40

passband

3

11

Trade-Off Between Temp. Stability & Bandwidth

T driftω

(a) Wider Transition Bandwidth

(b) Narrower Transition Bandwidth

T driftω

Efficient Use of Frequency Resources ⇔ Narrow Transition Bandwidth (Or Improve Production Yield)

12

0.80 0.82 0.84 0.86 0.88 0.90 0.92 0.94-30

-20

-10

0

10

20

LNA + SAW filter

Ideal Case

|S21

| (dB

)

f (GHz)

LNA

When S22 of PA output is NOT Negligible

RF Filter Causes Ripples

13

If Passive Filter is Symmetry and Loss-Less,

S22=S11, S12=S21, |S11|2+|S21|2=1, S11S21*+S11

*S21=0

212

2111 1|| SSjS −±= −

S22 and S11 are closely related!

High Q factor possesses Longer Time Delay.

Good Passive Filters can Generate Large Passband Ripples

14

-6 -5 -4 -3 -2 -1 0 1 2 3

56789

1011121314

Pout

(dB

m)

Pin (dBm)

with filter with S11=0

with filter

without filter

Influence of Filter S11 for Class AB PA

15

-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 20123456789

10111213

Pout

(dB

m)

Pin (dBm)

14.7-j10.8

35.9-j5.945.2-j2.3

Influence of Filter Impedance for Class AB PA

16

-6 -5 -4 -3 -2 -1 0 1 2 3 4 5

0.20.3

(1)(2)

PAE

Pin (dBm)-6 -5 -4 -3 -2 -1 0 1 2 3 4

67891011121314

(1)(2)

Pout

(dB

m)

Pin (dBm)0

0.40.50.60.70.8

(1)Capacitive Termination for Harmonics

(2) 50 Ω termination for Harmonics

Influence of Impedance for Harmonics for Class AB PA

17

R0V0

R0

R R0

P1

P

P3

P2

R0

P4 Filter

Filter

S11 Suppressor for RF Filters based on Quadrature Hybrids

18

0.80 0.82 0.84 0.86 0.88 0.90 0.92 0.94-60

-50

-40

-30

-20

-10

0S 1

1(d

B)

frequency (GHz)

0.80 0.82 0.84 0.86 0.88 0.90 0.92 0.94-60

-50

-40

-30

-20

-10

0

S 21

(dB

)

frequency (GHz)

Experimental Results

Using Huge Microstrip-Based Hybrids

(10x5 cm2)

19

Experimental Results

Using 1005 SMD-Based Hybrids

0.80 0.82 0.84 0.86 0.88 0.90 0.92 0.94-60

-50

-40

-30

-20

-10

0

frequency (GHz)

0.80 0.82 0.84 0.86 0.88 0.90 0.92 0.94-60

-50

-40

-30

-20

-10

0

frequency (GHz)

S 11

(dB

)

S 21

(dB

)

C12

C12C12

C12 L1

L1L2 L2

20

RF Filter BasicsRF Filter BasicsRF Filter Basics RF SAW & BAW Filters Major PlayersMajor PlayersMajor Players

ContentsContents

21

Surface Acoustic WaveSurface Acoustic WaveBulk Acoustic Wave (BAW):Longitudinal Wave (Primary Wave)

Transverse Wave (Share Wave, Secondary Wave)

Surface Acoustic Wave (SAW):

(Rayleigh SAW)Propagation of

Seismological Waves

22

Surface Acoustic Wave (SAW) Device

Vout

Vin

Piezoelectric substrate

Interdigital Transducers (IDT)

SAW

Mass Production by Photolithography Low loss, Miniature & Low price Operation inVHF-UHF ranges

Line width λ/4=0.5µm (f=2GHz)

23

Impulse Response

Independent Control of Amplitude and Phase Responses

SAW Transversal FiltersSAW Transversal Filters

24

Impulse Response Frequency Response

t f

t

t

∫+∞

∞−

−= dtjftthfH )2exp()()( π∫+∞

∞−

+= dfjftfHth )2exp()()( π

f

f

25

454137 49 53

10 dB/div

FREQUENCY (MHz)43.7541.7539.75 45.7547.75

1 dB/div

50ns/div

FREQUENCY (MHz)

SAW Transversal Filter for CATV

Ref. 15dB

26

8070605040302010

0

67.5 68 68.5 69 69.5 70 70.5 71 71.5 72 72.5Rel

ativ

e In

serti

on L

oss i

n dB

Frequency in MHz

ExperimentSimulation

SAW IF Filter for IS-95

Good Response but Higher Insertion Loss

27

SAW Resonator FilterSAW Resonator Filter

Mass Production by Photolithography High Frequency, Low Loss, High Stability Cheap(?), Small(?)

Interdigital Transducer (IDT)

Reflector (Al)λ

Piezo-Substrate （42oYX-LiTaO3)

28

Piezoelectric Material

+

-

C0 η

Mk-1

V F

i v

C0

L

R

C1

Analogies between V⇔F and I⇔v reduce toM⇔L, η⇔ R, k ⇔ 1/C

(a) Electric + Mechanical Circuit

Application of Electric Field to Piezoelectric Material,

(b) Electrical Equiv. Circuit

∫ ∝=++ VFvdtkvdtdvM η

29

Frequency

Adm

ittan

ce

ωr ωa

B

G

Resonance CharacteristicsResonance Characteristics

Resonance Frequency　ωr=1/ C1LAnti-Resonance Frequency　ωa=1/ L(C1

-1+C0-1)-1

30

Ladder-Type SAW FilterLadder-Type SAW Filter

Topology

Low Loss High Power Durability Moderate Out-of-Band Rejection

31

Performance of Ladder-Type SAW FilterPerformance of Ladder-Type SAW Filter

W-CDMA-Rx

-50-45-40-35-30-25-20-15-10-50

1900 2000 2100 2200 2300 2400-5

-4

-3

-2

-1

0

Tx Rx

Frequency (MHz)

Fujitsu FAR-F6CP-2G1400-L21M

Scat

terin

g Pa

ram

eter

S21

(dB

)

Scat

terin

g Pa

ram

eter

S21

(dB

)

32

1nH ( ≈ gold wire of 1mm length)

6Ω/mm @ 1GHz

1pF ( ≈ 1mm×1mm pad on LiNbO3 substrate)

150Ω/mm @ 1GHz

Influence of parasitic impedances is significant in GHz range!

33

S1 S2

P1 P3

S3

P2Ci Co

Filter Chip

Influence of Common ImpedanceInfluence of Common Impedance

Equivalent Circuit Origin of Lc

Ce1 Ce2 Ce3

Le1 Le1 Le1

Li Lo

Lc

Ce4

34

M

L2L1

M

L2-ML1-M

Influence of Mutual LInfluence of Mutual L

)()(

)()(

212

22

21

2

211

121

11

IIdtdM

dtdIML

dtdIL

dtdIMV

IIdtdM

dtdIML

dtdIM

dtdILV

++−=+=

++−=+=

35

λ/4

λ/4

TX-port

RX-port

Antenna-port

SAW filter, TX

SAW filter, RXstrip line

strip line

F re q u e n c y [M H z]

Att

enua

tion

[dB]

0

-2 0

-4 0

-6 018 0 0 19 0 0 20 0 0

T x ba n d Rx ban d

F re q u e n c y [M H z]

Att

enua

tion

[dB]

0

-2 0

-4 0

-6 018 0 0 19 0 0 20 0 0

T x ba n d Rx ban d

Antenna Duplexer for US PCS

Rx Band

Tx Band

Courtesy of Fujitsu Labs.

36

J.Tsutsumi, et al., Proc. IEEE Ultrason. Symp. (2004) pp. 954-958

Fujitsu Labs.

Bonding with Small Thermal Expansion Coef.

Temperature Compensation (1)

37

Temperature Compensation (2)

M.Kadota, et al., Proc. IEEE Ultrason. Symp. (2004) pp. 1970-1975 Murata MFG

Depositing SiO2 with Negative Temp. Coef.

38

Good Out-of-Band Rejection

Balun Function Transformer Function Low Loss Lower Power Durability

Symmetrical & Anti-

symmetricalResonances

Double Mode SAW (DMS) Filter

arsωωωω ωωωωr

ωωωω

Inse

rtio

n lo

ss (d

B)

Frequency

Electrically Isolated I/O

39

Structure of PitchPitch--Modulated IDT & ReflectorModulated IDT & ReflectorConventional Structure PitchPitch--Modulated StructureModulated Structure

IDT IDTREFECTOR

ModulatedModulated

ModulatedModulatedGap ControlledGap Controlled

Presented at IEEE 2004 UFFC Conf.

40

-8-7-6-5-4-3-2-10

800 850 900 950 1000 1050-80-70-60-50-40-30-20-10

0

Frequency [MHz]

Scat

terin

g pa

ram

eter

. S21

[dB

]

Scat

terin

g pa

ram

eter

. S21

[dB

]

DMS Filter with Modulated StructureDMS Filter with Modulated Structure

Fujitsu FAR-F5EB-942M50-B28E

41

Integrated RF Circuit Integrated RF Circuit

Current Antenna and RF Stage are Unbalanced

(a) Balanced I/O

(b) Unbalanced I/O

+

-

+-

42

Front-endBPF LNA

Inter-stageBPF IF-BPFMixer

Front-endBPF LNA IF-BPFMixer

Balun IF-Amp

IF-Amp

Discrete SAW Filter & Balun

Inter-stageBPF

SAW Filter with Balun Function

43

Vout+

Vout-

Vin

DMS Filter (Ideally No Common Signal)

Acoustically Coupled but Electrically Isolated

Common Signal Generation by Parasitics

44

Vout+

Vout-

Vin

Vin

Vout+Vout-

Z-conversion by DMS Filter

45

CSP for SAW Chip

By EPCOS

Embedded L

46

M.Goetz, C.Jones, J.Rao, K.Bhattacharjee and J.Flowers: "Advanced SAW Packaging for Modular Integration", Proc. 2nd International Symp. on Acoustic Wave Devices for Future Mobile Communication Systems (2004) pp. 145-150.

Wire-Based Packaging vs. CSP

47

(a) Substrate Etching (Fujitsu Labs.)

resonator

cavity

resonator

cavity

resonator

(b) Surface Micro-machining (Agilent, Epcos, ST Micro)

(c) Multi-Layer Reflector (Infineon, Philips), SMR (Solidly-Mounted Resonator)

Film Bulk Acoustic Resonator, FBAR

48

overlap Oxidepassivation

AlN

SiO2

SiO2

WSiNx

49R. Ruby, et al., IEEE Microwave Symp. (2004) pp.931-934

Ladder-Type FBAR FilterLadderLadder--Type FBAR FilterType FBAR Filter

By Agilent

50

Transversally Coupled Double-Mode Filter

Si

Electrodes

1:-1Rin C0

a CmLm Rma a

s CmLm Rms s

C0 RoutEin

Equivalent Circuit

1-Port Resonator When Parallel-Connected

Another 1-Port Resonator When Parallel-Connected with Inversion

Symmetrical & Antisymmetrical

Resonances

51

Fundamental Resonator by Quartz

Fundamental Resonator Filter on AT-cut Quartz (TOYOCOM TF2-D0AD6)

Anisotropic Etching of Quartz BulkGood Temperature StabilityUse of Single Crystal = High Q, High Uniformity

52G. G. Fattinger, et al., IEEE Microwave Symp. (2004) pp.927-930

Cascaded Coupled FBAR FilterCascaded Coupled FBAR FilterCascaded Coupled FBAR Filter

Electrically Isolated I/OBy Infineon

53

FBAR with Balun & Transformer Func.

50Ω:50Ω

50Ω:200Ω By Infineon

54M. Franosch, et al., IEEE Microwave Symp. (2004) pp.493-496

CSP for FBARBy Infineon

55

Agilents Latest Product/Technology: High Q Resonators and Filtersmanufactured in an “all-Silicon” package. Size 0.7 X 0.8 X 0.2 mm3

(GSM filter kit shown on a single kernel of short grain rice)

56

0

4.5 5.0 5.5 6.0

-40

-30

-20

-10

-50

Frequency (GHz)

Att

enua

tion

(dB

)

FBAR filter

SAW filter

Filter Response for Wireless LAN

Influence of Electrode Resistance Obvious for SAW at 5 GHz Range

FBAR Beneficial over 2 GHz?

Fujitsu Labs

57

Acoustic MigrationAcoustic MigrationStress-Induced Movement of Grain Boundary ⇒ Electrode Shortage

Electrode Scarcely Deformed in BAW Case

Countermeasure: Development of New Electrode Material System

58

1.3Frequency, f [GHz]

0.7 0.8 0.9 1 1.1

Inse

rtion

loss

[dB

]

0

10

20

30

40 1.2

Low Loss and Wideband SAW Filter Employing Cu-Grating/15oYX-LiNbO3 Substrate Structure

59

(a)Amplitude response (b) Group delay response

Constant-Group-Delay SAW Filter Using RSPUDTs

(a)

460 480 500 520 540 560 580

-70

-60-50

-40

-30

-20

-10

0

Frequency( MHz )

Inse

rtion

Los

s (d

B)

ExpSim

460 480 500 520 540 560 580100

150

200

250

300

350

Frequency (MHz)G

roup

del

ay (n

s)

60

RF Filter BasicsRF Filter BasicsRF Filter Basics RF SAW and BAR DevicesRF SAW and BAR DevicesRF SAW and BAR Devices Major Players

ContentsContents

61

EPCOS, Germany (RF+IF+Dup+FEM) Murata, Japan (RF+IF+Dup+FEM) Fujitsu, Japan (RF+IF+Dup) SEMCO, Korea (RF+Dup+FEM) SAWTEK, USA (RF+IF+Dup+FEM) Matsushita, Japan (Dup) Hitachi, Japan (FEM) Toyocom-Epson, Japan (RF+IF) Kyocera, Japan (RF+IF) NDK, Japan (RF+IF)

SAW Major PlayersSAW Major Players

62

Agilent Technology, USA Infineon Semiconductors, Germany Philips Semiconductors, Nederlands TFR Technologies (SAWTEK), USA Fujitsu, Japan EPCOS, Germany

FBAR Major PlayersFBAR Major Players

63

ST Microelectronics, France Toshiba, Japan Asahi Microsystem, Japan Sony, Japan Samsung, Korea Matsushita, Japan Ube Industries, Japan Asahi Glass, Japan Kinseki, Japan Hitachi, Japan Murata, Japan

FBAR DevelopersFBAR Developers

64

Intel, Israel Freescale, USA Skyworks, USA (?) RF MicroDevices, USA (?) NGK Insulators, Japan? Soshin Electric, Japan? Denso, Japan? Toppan Printing, Japan? Dai Nippon Printing, Japan? Other foundries?

FBAR Developers (continue)FBAR Developers (continue)